Internalized homophobia (IH) negatively impacts the mental health of adolescent sexual minority men (ASMM), while self-esteem is posited to bolster their mental health. In a repeated-measures study with 599 ASMM (Mean age = 16.2 [SD = 1.3]; 75.6% racial and ethnic minorities), longitudinal structural equation models investigated the relationships among IH, self-esteem, and mental health (depression and anxiety), as well as the mediating role of self-esteem. Higher self-esteem at earlier time points was significantly associated with lower anxiety and depressive symptoms. The hypothesized mediation pathways were not statistically significant. Subgroup analyses revealed that the protective effect of self-esteem against anxiety was significant for racial and ethnic minority ASMM but not for their non-Hispanic White counterparts. These findings highlight the need for tailored interventions that address the unique experiences of ASMM from diverse racial and ethnic backgrounds.